Method and apparatus for development of power



Oct. 1929- E. M. GILBERT 1,732,009

METHOD AND APPARATUS FOR DEVELOPMENT OF POWER Filed Nov. 3, 1927 2 Sheets-Sheet 1 715594405727 TIER/nos mr WITNESS IINVENTOR E-M.G '||ber1' ATTORNEY Oct. 15, 1929. E, GILBERT 1,732,009

METHOD AND APPARATUS FOR DEVELOPMENT OF POWER Filed. Nov. 3, 1927 2 Sheets-Sheet 2 150' {5 FWJ nnjnflfinnu l n H 'h'l' "M' am; 'iL u Aux ham 23 A IZ ,I4 I; k 1: u

Final Temp. of working 5120/11 leaving Gas Reheafer Abso/ufa Pressure liupen inch.

in fzum R e-h eater Temperafurg- Dagrees F of Flow of work/r19 sream 1h percenf ofmnrimum demand WITNESS F lNVEN TOR (5L5. 1.9.3. BY E.M.G||ber1' ATTORNEY Patented Oct. 15, 1929 UNITED STATES PATENT OFFICE ERNEST M. GILBERT, OF WYOMISSING, PENNSYLVANIA, ASSIGNOR T0 W. S. GABSTOW & COMPANY, A CORPORATION OF DELAWARE METHOD AND APPARATUS FOR DEVELOPMENT OF POWER Application filed November 3, 1927. Serial No. 230,876.

My invention relates to a method and apparatus for developing power, more particularly to multiple stage power development, and it has for an object to reheat the motive fluid between stages in a manner to secure improved performance.

It is recognized in the steam turbine art that a turbine designed for operation with working steam containing the maximum permissible number of heating units will be relatively more efficient than a turbine designed for operation with working steam of less heatcontent; and, it is, therefore, well established that improved efficiency may be had by operating at relatively high initial temperatures and pressures as well as by reheating between stages. Also, for a given turbine operating with a predetermined output, maximum economy is realized, when steam is delivered to the turbine at predetermined pressure and temperature. Where steam is supplied at substantially constant pressure and temperature to the Initial stage of the first of a pair of turbines arranged in series, with no provision for reheating between the last stage of the first turbine and the first stage of the second turbine, the temperature of steam entering the initial stage of the second turbine will be a function of the quantity of steam supplied to the apparatus; and it Will be evident that better operation of the second turbine may be secured if steam is admitted thereto at a. temperature most suitable to its design. Accordingly, therefore, it is a further and more particular object of my invention. not only to reheat between stages or units, but to reheat in such a way that the reheated steam shall have a substantially uniform temperature so that the second turbine may be operated at an efficiency suitable to its design even though there may be wide "ariations in load.

Iieretofore. reheating between turbine stages or units has been effected either by a steam reheater utilizing superheated steam as the heating medium or by a reheater utilizing products of combustion as a heating medium. In accordance with my invention, I provide first and second stage reheaters, the

t stage utilizing steam as a heating medium and the second stage utilizing products of combustion as a heating medium. With this arrangement, as the load decreases, the work of heating by the steam reheater increases and the work of heating by the gas reheater decreases so that the two operating in series compensate for each other; and, in order that a more uniform temperature may be had over a fairly wide operating range, and in order to effect the compensating effect just referred to, I associate a thermostat with the line leading from the gas reheater to the second turbine, this thermostat serving to control a valve in the steam supply line for the steam reheater so that the heating effect of the steam reheater may be varied so as to maintain a substantially constant temperature of steam supplied to the second turbine. It is, therefore, a further object of my invention to provide power plant apparatus having a series arrangement of turbines with reheater apparatus disposed and operated in the manner just stated in order to secure more efficient operation of the second turbine of the series with variation in load.

My improved arrangement of reheating between first and second stages or units of a turbine installation finds particular utility where high pressure steam is used. So far as I am aware, it is customary with plantsutilizing steam at initial pressure in excess of 600 lbs, to reheat at substantially constant pressure, that is, the high pressure turbine exhausts to a steam main, the latter being supplied with additional steam from boilers and supplying turbines of lower pressure. Suitable reheating apparatus is used in conjunction with a main of this character in order that steam of a suitable temperature may be supplied to the turbines of lower pressure. In such an arrangement, control is efl'eeted by cutting in and out and by governing the turbines of lower pressure, the idea being to maintain the pressure of the main at substantially constant value so that sufiicient steam may be supplied under conditions of temperature and pressure suitable to the design of the turbines of lower pressure. In other Words only a portion of the total steam is generated a high pressure and used in the high pressure turbine, the -high pressure turbine being intended to operate at all times and passing as much steam as it may from the high pressure source to the main, variations in load being taken up by suitably controlling or governing the turbines of lower pressure. In accordance with my invention, I provide a power plant utilizing a highpressure turbine arranged in series with a turbine of lower pressure so that all of the steam is generated at high pressure and passed through the high and low pressure turbines in series. The high pressure turbine is, therefore, controlled or governed in order that the quantity of steam passing may be varied in accordance with the load; however, in order that the low pressure unit may operate at a high eificiency, I arrange my improved reheatin apparatus between the high pressure an the low pressure unit so that reheated steam may be supplied to the low pressure unit at substantially a constant temperature even though there may be a wide variation in load. Preferably, I superheat and reheat the working steam to a point suitable to the materials of construc tion used. For example, I indicate a temperature of 750 F., this being the present limit for available materials. Accordingly, it is a further object of my invention to provide an improved high pressure steam power plant and a method of operation thereof such that all steam generated at the high pressure may pass in series through the turbine units, the steam being reheated between the units in such a way as to maintain a substantially constant temperature of steam entering the low pressure unit.

These and other objects are effected by my invention as will be apparent from the following description taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a diagrammatic View of power plant apparatus showing my improvement ap plied thereto;

Fig. 2 is a diagrammatic view which shows the power plant apparatus more completely; and

Fig. 3 is a diagrammatic view illustrating the principle of operation of my reheating ap aratus.

eferring first to Fig. 2, I show a steam generator 10 and a superheater 12 arranged in heat-exchange relation with respect to the furnace chamber 13 provided with suitable combustion apparatus 14, air for the combustion apparatus preferably being heated by the prehcater 15. Steam generated in the boiler or generator 10 passes through the superheater 12 and then, by the line 16, to the inlet of the high-pressure turbine 17. Steam exhausted from the high-pressure turbine 17 is supplied by the line 18 for passage in series through the steam reheater 19 and the gas reheater 20; and, after being reheated,

the steam is conducted by the line 21 to the inlet of the low pressure turbine 22, steam being bled from the turbine 22 to supply heaters 23 and 24, the remainder of the steam passing through the turbine 22 being discharged to the condenser 25. Condensate from the condenser 25 passes in series through the heaters 23, the jet heater 26, the lower pressure stages 27 of the pump 28, the heaters 24 and 29, the higher pressure stages 30 of the pump to the economizer 31 and then to the boiler or generator 10.

My invention is concerned largely with the arrangement and operation of the high and low-pressure turbines, together with the reheating apparatus which operates to maintain the temperature of steam supplied to the low-pressure turbine 22 at substantially constant temperature over fairly wide variations in load, and this will now be described more in detail.

Referring now to Fig. 1, in order that my arrangement of turbines and reheating apparatus may be better understood, it will be noted that the steam reheater 19 is arranged above the boiler or generator 10 and that it is provided with a heating coil 33 connected to the boiler or generator by supply and return lines. As shown, circulation is obtained through the steam reheater 19 in a thermosiphon manner, that is, steam passes from the boiler or generator 10 through the supply line 34 and it is cooled or condensed in the coils 33, the condensate returning to the generator by the line 35. In this way, it is possible to obtain adequate circulation of heating saturated steam without a pump; however, in case the reheater should be differently disposed or if superheated steam should be used as the heating medium a circulating pump would be used.

With the present arrangement, as I contemplate generating steam at a relatively high pressure, for example, 1200 lbs., it will be apparent that I am able to use saturated steam in the heater 19 for heating purposes as the temperature corresponding to such high pressure will be suficiently above the temperature of steam exhausted from the high-pressure turbine 17 to impart heat effectively to the steam passing from the high-pressure turbine 17 through the heater 19. After the initial stage of heating is effected in the steam heater 19, the motive or working steam then passes through the line 36, thence through the gas reheater 20, and then through the line 37 to the low-pressure turbine 22. As shown, the gas reheater 20 is located in a gas space of the combustion apparatus which is surrounded by boiler or generator tubes; however, it will be obvious that the gas reheater may be located in any suitable manner so long it is capable of receiving suiiicient heat from products of combustion.

With a decrease in load, the steam reheater is capable of heating each unit of weight of working steam to a higher point. The two reheaters operate in series so as to maintain a substantially constant temperature of working steam supplied to.the second turbine under variable load conditions. In order that steam furnished from the gas reheater 20 to the low-pressure turbine 22 may be supplied to the latter at substantially constant temperature, thermostatic apparatus 38 is associated with the line 37 and serves to control a relay 39, the latter controlling the position of a valve 40 in the supply line 34 for the steam heater. Hence, it will be seen that the gas heater 20 is at all times fully effective but dependent upon conditions of combustion and that variations in its capacity are taken care of by changing the capacity of the steam reheater 19, the thermostatic apparatus operating to cause more or less steam to pass through the steam reheater as determined by the temperature of steam passing through the line 37 to the low-pressure turbine 22.

The principle of operation of the reheating apparatus will be evident from a consideration of Fig. 3. If the load on the installation decreases, the tem erature and pressure of working steam entering the steam reheater decline as indicated by the curves A and E. If the temperature decreases, as indicated by the curve A, this means an increased temperature difference between the temperature of the saturated heating steam, as indicated by line C, and the tem erature of the working steam as indicate by the curve A, that is, the heat head, as indicated by the ordinate distance between A and C increases with a decrease in rate of flow of working steam. Therefore, per unit of working steam, the steam reheater has greater heating capacity with a decrease in load, and the resultant rise in temperature of the steam passing through the steam reheater is greater, as indicated by the ordinate distance between the curves A and B. With a decrease in .rate of flow of working steam, that is, with a decrease in load, the amount of heat added to the working steam by the gas reheater will decrease, and with an increase in load the amount of heat added by the gas reheater will increase, substantiallyI as indicated by the curves B and D. ence, under variable load conditions, the shaded area between the curves A and B indicates the work of heating done in the steam reheater while the shaded area between the curves B and D indicates the work of heating done in the gas reheater. The thermostat associated with the discharge line from the gas .reheater is effective to control the suppl of saturated heating steam to the steam re eater, thereby making it possible for the two reheaters operating in series to reheat working steam to a predetermined temperature with fairly wide variations in load.

From Fig. 3, it will be noted that, if saturated steam from the steam generating unit is used as the heating medium in the steam reheater, such steam must be generated at a sufficiently high pressure that the corresponding temperature will be sufliciently higher" than the temperature of working steam exhausted from the high-pressure turbine to be effective as a heating medium for the latter. While saturated steam may be used for heating in this way without the necessity of circulating pump means, it will be obvious that where steam is generated at a lower pressure or where the temperature difference between the saturated steam and the temperature of steam entering the steam reheater is not sufficiently great, then superheated steam may be used as a heating medium for the steam reheater, in which case, of course, it would be necessary to employ circulating pump means to maintain the heating circuit.

From the foregoing, the operation of the apparatus and the method described will be clearly understood. I provide a highpressure turbine from which steam exhausts and passes in series through a steam reheater and gas reheater and from the gas reheaterthe motive steam passes into a lowpressure turbine. The steam and gas reheaters operate complementally to maintain a substantially constant temperature of steam supplied to the low-pressure turbine so that, even though the load or demand may vary over a wide range, nevertheless, the temperature of motive steam supplied to the low-pressure turbine will be maintained approximately constant and suitable to the operation of the latter turbine at high el'liciency. In this way, the desirable objective of supplying motive fluid to the turbine units at as high a temperature as possible consistent with materials of which the turbines are constructed is achieved.

Hence, it will be seen, that I have-provided a power developing system in which steam is admitted to the power developing stages or units at temperatures which are as high as consistent with the materials used in the construction of the apparatus, that is, I utilize working steam having the highest feasible heat content for each stage of power development, thereby improving the performance. Stated in another way, I secure improved thermal efiiciency by providing that the heat content of working steam entering the second power development unit or stage shall be regulated in such a manner as to make available in such second stage the maximum desirable number of heat units per pound of working steam.

While I have referred to high and lowpressure turbines herein, it will be apparent that the reheating apparatus may be usedbetween any suitable power-developing stages or elements, this invention being characterized by such an arrangement of complementary reheating devices that working steam of substantially uniform temperature or heat content per unit of weight may be supplied to the second power-developing stage under varying load conditions.

Whenever the term saturated steam is used herein, it is to be understood that such term refers to the condition of steam as it leaves the boiler or generator and it is to be understood that, with certain types of boilers, the steam may be slightly superheated.

While I have shown my invention in but one form it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is 1. In a power plant, the combination of first and second power developing stages, a

furnace chamber, a steam generator ar-' ranged 1n heat exchange relation with respect to the chamber, a first reheater supplied with saturated steam from the generator, a second reheater disposed in heat exchange relation with respect to the chamber, means for passing steam discharged from the first stage in series through the first and second reheaters to the second stage, and means for regulating the rate of supplying of saturated heating steam to the first reheater.

2. In a power plant, the combination of first and second power developing stages, a furnace chamber, a steam generator arranged in heat exchange relation with respect to the chamber, a first reheater supplied with saturated steam from the generator, a second reheater disposed in heat exchange relation with respect to the chamber, means for passing steam discharged from the first stage in series throu h the first and second reheaters to the seconcI stage, and means responsive to the temperature of steam passing from the second reheater to the second stage for controlling the supply of heating steam to the first reheater.

3. In a power plant, the combination of first and second turbines, combustion apparatus, a steam generator for supplying steam to the first turbine and heated from the combustion apparatus, a firstreheater supplied with heating steam from the generator, a second reheater heated from the combustion apparatus, means for passing steam exhausted from the first turbine in series through the first and second reheaters to the second turbine, and means for controlhausted from the first stage in series through the first and second reheaters to the second stage, and means for controlling the saturated steam supplied to the first reheater so as to maintain the temperature of steam supplied to the second stage substantially constant.

5. In a power plant, the combination of first and second turbines, combustion apparatus, a steam generator heated from the combustion apparatus, means including a superheater for supplying steam from the generator to the initial stage of the first turbine, a first reheater arranged above the generator, supply and return lines for connecting the first reheater and a generator, a control valve in the supply line, a second reheater heated from the combustion apparatus, means for passing steam exhausted from the first turbine in series through the first and second reheaters to the initial stage of the second turbine, and means responsive to the temperature of steam passin from the second reheater to the second turbine for controlling said control valve.

6. In a power plant, the combination of first and second power-developing stages, reheating means, means for passing steam exhausted from the first stage through the reheating means to the second stage, means providing for the application of heat to the reheating means, and means responsive to the temperature of steam supplied to the second stage for controlling the application of heat to said reheatin means.

7. The combination with multiple stage power-developing apparatus and a steam generator, of reheating means disposed between stages of said apparatus and including a reheater disposed above the generator, means providing for the supply of saturated steam from the generator to the reheater as heating medium for the latter, and means res onsive to the temperature of steam passing rom the reheating means to the second stage to control the supply of heating steam to said reheater.

8. In a power plant, the combination with first and second power-developing stages, of a pair of reheater units arranged in series between said stages, means providing for the heating of said reheater units by separate media, and means for controlling the rate of supplying heating medium to one of said units in order to maintain a substantially constant temperature of motive fluid supplied to the second stage.

9. In a power plant, the combination with first and second power-developing stages, of a pair of reheater units arranged in series between said stages, means providing for the heating of said reheater units by separate media, and means responsive to the temperature of motive fluid passing from the reheater units to the second stage for controlling the rate of supplying heating medium to one of said units in order to maintain a substantially constant temperature of motive fluid supplied to the second stage.

10. The combination with first and second power-developing stages and means for supplying steam to the first stage at a tem' perature of the order of 750 F., of a pair of reheaters arranged to have steam pass therethrough in series on its way from the first to the second stage, means for supplying heating medium to one of the reheaters, means for supplying a separate heating medium to the other of said reheaters, and means responsive to the temperature of steam passin from the reheaters to the vsecond stage or controlling the supply of heating medium-to one of said reheaters in order to maintain the steam passing from the reheaters to the second stage at a temperature of the order of 750 F.

In testimony whereof, I have hereunto subscribed my name this 31st day of October,

ERNEST M. GILBERT.

media, and means for controlling the rate of supplying heating medium to one of said units in order to maintain a substantially constant temperature of motive fluid supplied to the second stage.

9. In a power plant, the combination with first and second power-developing stages, of a pair of reheater units arranged in series between said stages, means providing for the heating of said reheater units by separate media, and means responsive to the temperature of motive fluid passing from the reheater units to the second stage for controlling the rate of supplying heating medium to one of said units in order to maintain a substantially constant temperature of motive fluid supplied to the second stage.

10. The combination with first and sec ond power-developing stages and means for supplying steam to the first stage at a temperature of the order of 750 F., of a pair of reheaters arranged to have steam pass therethrough in series on its way from the first to the second stage, means for supplying heating medium to one of the reheaters, means for suppl i-ng a separate heating medium to the ot er of said reheaters, and means res onsive to the temperature of steam passin rom the reheaters to the second stage or controlling the supply of heating medium to one of said reheaters in order to maintain the steam passing from the reheaters to the second stage at a temperature of the order of 750 F.

In testimony whereof, I have hereunto subscribed my name this 31st day of October,

ERNEST M. GILBERT.

CERTIFICATE or CORRECTION.

Patent No. 1,732,009.

ERNEST M. GILBERT.

It is hereby patent was erroneously written and printed as whereas said name should have been written and printed as -b the fa i d ltzltdrs lft zdl sht iuld he read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 12th day of November, A. D. 1929.

"W. S. Garstow & Company",

"W. S. Barstow &

' M. J. Moore,

(Seal) Granted October 15, 1929, to

certified that the name of the assignee in the above numbered records of assignments in this office; and that the Acting Commissioner of Patents. 

